1. Field of the Invention
Embodiments of the present disclosure relate to an ink for ink-jet recording in which colored particles are employed as a coloring agent.
2. Description of the Related Art
As an ink for ink-jet recording, a dye ink in which a dye is dissolved in an ink solvent composed of water and a water soluble organic solvent are widely used. However, the dye ink easily cause blurring on printing materials. In view of this, so-called a particle ink have been proposed in which colored particles having a volume average diameter in the range of approximately 0.01 μm to 20 μm are employed as coloring agents.
It is desirable in such a particle ink that the specific gravity of the ink solvent be the same as that of the colored particles in order to prevent the colored particles from separating out from the ink solvent. Therefore, a density adjusting agent is used. The use of the density adjusting agent theoretically allows the densities of the ink solvent and the colored particles to be adjusted to the same level. However, a few percent difference in density between the ink solvent and the colored particles may occur due to measurement errors during preparation of the ink solvent, temperature variations, or the like.
The influence of the difference in density on the sedimentation velocity or floating velocity of the particles increases as the particle diameter increases. Because the particle diameter distribution of conventionally used colored particles is broad, large particles adversely affect the storage stability of the ink. In addition to this, large particles having diameters of approximately ⅕ to ⅓ or more of the diameter of the ink jet nozzles may also cause a problem in that the nozzles may become clogged temporarily. Furthermore, after the ink droplets land on the paper, relatively small particles of sub-micron sizes may penetrate the gaps between the paper fibers with the ink solvent. Therefore, a problem arises in that blurring can be observed with the naked eye and the edges of the image lines may be disturbed.